1. Field of the Invention
The present invention relates to a wiring patterned film and its production. Specifically, the invention relates to a wiring patterned film and its production wherein a gold lead which extends from a wiring pattern formed on the adhesive side of a resin film adhered to the side of a semiconductor element on which an electrode terminal is formed, and which bridges a window section opening on the resin film, is cut off at a prescribed location facing the window section and is bent so that the lead tip is connected to the electrode terminal.
2. Description of the Related Art
In recent years, practical applications of chip size packages, such as that shown in FIG. 3, which are small and can be made with small mounting areas, are being attempted as semiconductor devices built into portable electronic devices such as cellular phones (see, for example, WO 94/03036).
This type of chip size package has a wire patterned film 11 (hereunder sometimes referred to simply as "film 11 "), consisting of a wiring pattern 14 formed on one side of a resin film 16, on one side of a semiconductor element 10 on which is formed an electrode terminal 20 around the edges, and adhered at a region inward from the region where the electrode terminal 20 is formed, via an elastomer layer 12 which is an elastic resin layer. The film 11 has a smaller area than the side of the semiconductor element 10 on which it is adhered, and a lead made of gold (hereunder referred to as "gold lead") 18 extends from one end of the wiring pattern 14 consisting of a gold layer and copper layer formed on the adhesion side with the elastomer layer 12, to the outer edge of the resin film 16.
This gold lead 18 is bent so that the lead tip is connected to the electrode terminal 20 of the semiconductor element 10 while it is sealed, together with the electrode terminal 20 etc., by a sealing resin 22.
Also, at an opening 23 which reaches the back side surface at the other end of the wiring pattern 14 formed on the resin film 16, there is provided a bump 24, as an external connection terminal, formed by a plated or soldered ball or the like.
The film 11 is manufactured by the process illustrated in FIGS. 4A to 4F. In these illustrations, a copper foil 32 attached to one side of a resin film 16 is coated with an organic polymer resist layer 34 (hereunder sometimes to be referred to simply as "resist layer 34") and subjected to light exposure and development, so as to expose the portion of the copper foil 32 on which the wiring pattern 14 and gold lead 18 are to be formed (FIGS. 4A, 4B). The exposed areas of the copper foil 32 are coated with an electrolytic gold plating to form gold plated sections 36 (FIG. 4C).
Also, after the coated resist layer 34 is removed and window sections 23, 23 are formed, which expose the back side of the copper foil 32 at prescribed locations on the other side of the resin film 16, bumps 24 are formed by electrolytic nickel plating (FIG. 4D). The opposite side of the resin film 16 is covered with a mask at this time.
Next, the sections of the resin film 16 on which the gold leads 18 are to be formed are removed by laser light, to form gold lead-formed sections 38 where the back side of the copper foil 32 is exposed (FIG. 4E).
Then, by using chemical etching or the like on the gold lead-formed sections 38 to remove the copper foil 32 where the back side is to be exposed, it is possible to form wiring patterns 14 and gold leads 18 (FIG. 4F). In this step, the copper foil 32 where the back side is exposed is removed at the gold lead-formed sections 38, forming window sections 40 bridged by the gold leads 18 consisting of only the gold layer.
Thus, for each wiring pattern 14 and gold lead 18 which are formed in connection, the wiring pattern 14 consists of a double layer of a copper layer and gold layer, while the gold lead 18 consists of only the gold layer. The gold lead 18 can therefore be easily bent.
In the step shown in FIG. 4F, the copper foil 32 is also simultaneously removed on the other side of the resin film 16 so that the wiring pattern 14 is not formed there.
To manufacture of a semiconductor device using a wiring patterned film 11 on which such a wiring pattern 14 and gold lead 18 are formed, an elastomer layer 12 is used to connect the side of the resin film 16 on which the wiring pattern 14 is formed to the side of the semiconductor device 10 on which the electrode terminal is formed.
Next, the gold lead 18 bridging the window section 40 is cut at a prescribed location and bent with a bonder (not shown), while the lead tip of the gold lead 18 which has been cut is connected to the electrode terminal 20 of the semiconductor device 10, after which the gold lead 18 and electrode terminal 20 are sealed with a sealing resin 22.
Incidentally, notches 42 are formed at prescribed locations on each of the gold leads 18 as shown in FIG. 5, in order to facilitate cutting of the gold lead 18 when the gold lead 18 bridging the window section 40 is cut.
In this type of conventional wiring patterned film 11, it is necessary to form the notches 42 to a minimum prescribed depth in the widthwise direction of the gold leads 18 in order to ensure satisfactory cutting of the gold leads 18.
However, because deeper notches 42 are more difficult to form and reduce the mechanical strength of the gold leads 18, the notches 42 must by necessity be made shallow. This in turn reduces the cuttability of the gold leads 18.
In addition, when the gold leads 18 are fine as in the case of high-density gold leads 18 required for highly integrated semiconductor elements 10, the depth of the notches 42 must be made even more shallow.